Elastomers are one of the principal ingredients of a chewing gum base and thus in turn one of the principal ingredients of a final chewing gum product. Typically, a chewing gum base is made separately from the final chewing gum, although there are some systems which are capable of producing a final chewing gum product in one continuous process.
A chewing gum composition typically comprises a water-soluble bulk portion, a water-insoluble chewing gum base portion, and typically water-insoluble flavoring agents. The insoluble gum base generally comprises elastomers, elastomer solvents, plasticizers, waxes, emulsifiers, and inorganic fillers. The water-soluble portion dissipates with a portion of the flavoring agent over a period of time during chewing. The gum base portion is retained in the mouth throughout the time that the product is chewed.
The batch method of producing chewing gums has long been considered the standard for producing chewing gums, as well as gum bases, on a commercial scale. The batch processes, however, which typically used Sigma-blade mixers, tend to be labor-intensive and produce chewing gums of varying consistency.
Various efforts have been undertaken to try to simplify and reduce the time required for gum base and chewing gum manufacture, as well as to prepare gum base and gum products which have better and more consistent properties. For example, the use of continuous extruders to make a final chewing gum product are shown in U.S. Pat. No. 5,135,760 to Degady et al., U.S. Pat. No. 5,045,325 to Lesko et al., and U.S. Pat. No. 4,555,407 issued to Kramer et al. Also, there are several processes in the art for continuously producing a chewing gum base with the use of a continuous extrusion machine. These are disclosed, for example, in U.S. Pat. Nos. 5,419,919 and 5,486,366, both to Song et al.
The continuous gum base processes and final chewing gum product processes disclosed in these patents typically utilize a continuous extrusion machine, such as a twin-screw extruder. Continuous extrusion machines which can be used for producing a chewing gum base or a final chewing gum product, or both, include extruders from Japan Steel Works, Leistriztz, Werner & Pfleiderer Corp., and Buss Mfg. Co., WLS, Togum and Baker Perkins. These extruders typically have several different feed inlets where the ingredients are added, and the elongated screws inside the barrels of the extruders are equipped with different types of mixing and blending elements.
While different equipment manufacturers make different types of screw elements, the most common types include conveying elements, compression elements, reverse conveyance elements, homogenizing elements (such as shearing disks and toothed elements), and kneading disks and kneading blocks. These various types of elements, and other elements typically used in extrusion machines, especially twin screw extruders, are well known in the art and commercially available. The is elements are often specifically designed for the particular type of extruders utilized. In this regard, elements intended for similar functions will vary in design depending on the type of extruder for which they are intended.
Whether a batch-type processor or a continuous extruder-type processor is used to produce the chewing gum and gum base products, it is important to provide the various ingredients for these products in an optimum form and condition. This improves the speed and efficiency of the final processing. In this regard, ingredients such as the fillers, elastomers, plasticizers, oils, waxes, and the like, often require special handling or preparation prior to being included in the batch or extrusion process.
Preparation of the ingredients is especially important where a continuous extrusion processor is utilized. The ingredients supplied to the continuous extrusion apparatus are preferably provided in the optimum size, shape, condition and temperature for ease of handling, insertion and intermixing with the other ingredients in the extruder. Also, due to the properties of some of the various ingredient materials, it is necessary to pre-prepare or pre-blend them in order to allow them to be inserted in the extruder in the best possible condition.
As indicated, one important component of a gum base is the elastomeric portion which can include natural elastomers, synthetic elastomers, or combinations thereof. This element of the gum base is important in that it provides the insoluble body with resiliency to recover from deformation caused by chewing. In preparing gum base, it is important that other components which are included in the base composition to effect various characteristics of the resulting chewing gum, be thoroughly mixed with the elastomeric portion so that the entire gum base product will retain proper resiliency as a homogeneous phase.
Solid elastomers suitable for use in chewing gum bases and final chewing gum products include synthetic gums or elastomers such as butadiene-styrene copolymer, polyisobutylene, and isobutylene-isoprene copolymer, as well as natural gums or elastomers such as chicle, natural rubber, jelutong, balatea, guttapercha, lechi, caspi, sorva, or mixtures thereof.
Polyisobutylene is commonly used as one of the elastomer components for the gum base. Polyisobutylene adds "chewability" to the final gum product since many elastomeric materials, such as rubber, are hard to chew. Polyisobutylene materials are commercially available, for example, from Ritchem Corp. and Exxon Corp. (VISTANEX.RTM.).
Polyisobutylene and other elastomeric materials having high molecular weights, e.g. greater than 30,000, are difficult to work with in a commercial process. These materials are difficult to handle, melt, grind up and cut into smaller pieces due to their viscosity, consistency and characteristics. The difficulties in processing these materials are compounded when a continuous extrusion process is utilized where the materials need to be added in a predetermined amount and at a predetermined state and temperature.
When melting and processing these elastomeric materials, such as polyisobutylene, it is important not to trap air in the molten or liquified materials. Entrapped air prevents accurate and efficient metering of the material into a continuous extruder. Air entrapped also encourages undesirable oxidation of the material.
In batch-type processes, the high molecular weight elastomeric materials can be utilized more easily than with extruders. With batch-type processes, the bales, slabs or cylinders of material are simply inserted in the batch mixing tank and allowed to melt over time and mix with the other components in the tank.
In order to melt these materials, it is typically necessary to heat them in excess of 250-300.degree. F. In order to utilize these materials in a chewing gum or gum base processing system using a continuous extrusion apparatus, it is necessary to also maintain them at such elevated temperatures in order for them to stay in a liquid condition. Such elevated temperatures, however, if used for any length of time in the main extruder, could adversely affect other ingredients in the system.
It is a general object of the present invention to provide an improved method and apparatus for the production of chewing gum products and gum base products. It is also an object of the present invention to provide an improved method and apparatus for preparation of high molecular weight elastomeric materials, such as polyisobutylene, in order to facilitate improved processing of chewing gum and gum base products.
It is still another object of the present invention to provide a method and apparatus for continuously melting and storing elastomeric materials, such as polyisobutylene. It is another object of the present invention to provide an improved process and apparatus for feeding high molecular weight elastomeric materials, such as polyisobutylene, in a liquid or melted condition into a chewing gum or gum base processing system which utilizes a continuous extruder.
These and other objects, benefits and advantages are met by the present invention which is detailed in preferred form in the following description.